1. Field of the Invention
The present invention relates to a photoelectric conversion apparatus, a focus detection apparatus, and an image capturing system.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2011-130135 discloses a configuration of an autofocus (hereinafter referred to as AF) sensor in which a switch for connection to a common output line is disposed in a feedback path of a differential amplifier. This configuration can reduce the influence of voltage fluctuation due to switch resistance and enhance the accuracy of detection of the largest value and the smallest value of AF signals.
The method of driving disclosed in Japanese Patent Laid-Open No. 2011-130135 produces a period in which no feedback path is formed, so that a negative input terminal of an operational amplifier of the differential amplifier comes to a floating state, and the output signal changes toward a power source voltage or a ground potential.
Such a period can produce the following situations. A first situation is that the response time, that is, a signal read rate, decreases because it takes much time for the potential to converge to a predetermined value if signal reading is started in the state in which the output signal is at a power source voltage or a ground potential. A second situation problem is that the potential of the negative input terminal can change out of the input operation range of the operational amplifier due to crosstalk from a peripheral circuit. This can also reduce the response speed because it takes a much time for the potential of the negative input terminal to reach the predetermined value.